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Galambos AR, Papp ZT, Boldizsár I, Zádor F, Köles L, Harsing LG, Al-Khrasani M. Glycine Transporter 1 Inhibitors: Predictions on Their Possible Mechanisms in the Development of Opioid Analgesic Tolerance. Biomedicines 2024; 12:421. [PMID: 38398023 PMCID: PMC10886540 DOI: 10.3390/biomedicines12020421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/06/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
The development of opioid tolerance in patients on long-term opioid analgesic treatment is an unsolved matter in clinical practice thus far. Dose escalation is required to restore analgesic efficacy, but at the price of side effects. Intensive research is ongoing to elucidate the underlying mechanisms of opioid analgesic tolerance in the hope of maintaining opioid analgesic efficacy. N-Methyl-D-aspartate receptor (NMDAR) antagonists have shown promising effects regarding opioid analgesic tolerance; however, their use is limited by side effects (memory dysfunction). Nevertheless, the GluN2B receptor remains a future target for the discovery of drugs to restore opioid efficacy. Mechanistically, the long-term activation of µ-opioid receptors (MORs) initiates receptor phosphorylation, which triggers β-arrestin-MAPKs and NOS-GC-PKG pathway activation, which ultimately ends with GluN2B receptor overactivation and glutamate release. The presence of glutamate and glycine as co-agonists is a prerequisite for GluN2B receptor activation. The extrasynaptic localization of the GluN2B receptor means it is influenced by the glycine level, which is regulated by astrocytic glycine transporter 1 (GlyT1). Enhanced astrocytic glycine release by reverse transporter mechanisms as a consequence of high glutamate levels or unconventional MOR activation on astrocytes could further activate the GluN2B receptor. GlyT1 inhibitors might inhibit this condition, thereby reducing opioid tolerance.
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Affiliation(s)
- Anna Rita Galambos
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
| | - Zsolt Tamás Papp
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
| | - Imre Boldizsár
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
| | - Ferenc Zádor
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
| | - László Köles
- Department of Oral Biology, Semmelweis University, H-1089 Budapest, Hungary;
| | - Laszlo G. Harsing
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
| | - Mahmoud Al-Khrasani
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvá-rad tér 4, H-1445 Budapest, Hungary; (A.R.G.); (Z.T.P.); (I.B.); (F.Z.)
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Cieślik P, Wierońska JM. Regulation of Glutamatergic Activity via Bidirectional Activation of Two Select Receptors as a Novel Approach in Antipsychotic Drug Discovery. Int J Mol Sci 2020; 21:ijms21228811. [PMID: 33233865 PMCID: PMC7699963 DOI: 10.3390/ijms21228811] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 11/10/2020] [Accepted: 11/16/2020] [Indexed: 12/14/2022] Open
Abstract
Schizophrenia is a mental disorder that affects approximately 1-2% of the population and develops in early adulthood. The disease is characterized by positive, negative, and cognitive symptoms. A large percentage of patients with schizophrenia have a treatment-resistant disease, and the risk of developing adverse effects is high. Many researchers have attempted to introduce new antipsychotic drugs to the clinic, but most of these treatments failed, and the diversity of schizophrenic symptoms is one of the causes of disappointing results. The present review summarizes the results of our latest papers, showing that the simultaneous activation of two receptors with sub-effective doses of their ligands induces similar effects as the highest dose of each compound alone. The treatments were focused on inhibiting the increased glutamate release responsible for schizophrenia arousal, without interacting with dopamine (D2) receptors. Ligands activating metabotropic receptors for glutamate, GABAB or muscarinic receptors were used, and the compounds were administered in several different combinations. Some combinations reversed all schizophrenia-related deficits in animal models, but others were active only in select models of schizophrenia symptoms (i.e., cognitive or negative symptoms).
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Wang HY, MacDonald ML, Borgmann-Winter KE, Banerjee A, Sleiman P, Tom A, Khan A, Lee KC, Roussos P, Siegel SJ, Hemby SE, Bilker WB, Gur RE, Hahn CG. mGluR5 hypofunction is integral to glutamatergic dysregulation in schizophrenia. Mol Psychiatry 2020; 25:750-760. [PMID: 30214040 PMCID: PMC7500805 DOI: 10.1038/s41380-018-0234-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 06/18/2018] [Accepted: 07/09/2018] [Indexed: 11/19/2022]
Abstract
Multiple lines of evidence point to glutamatergic signaling in the postsynaptic density (PSD) as a pathophysiologic mechanism in schizophrenia. Integral to PSD glutamatergic signaling is reciprocal interplay between GluN and mGluR5 signaling. We examined agonist-induced mGluR5 signaling in the postmortem dorsolateral prefrontal cortex (DLPFC) derived from 17 patients and age-matched and sex-matched controls. The patient group showed a striking reduction in mGluR5 signaling, manifested by decreases in Gq/11 coupling and association with PI3K and Homer compared to controls (p < 0.01 for all). This was accompanied by increases in serine and tyrosine phosphorylation of mGluR5, which can decrease mGluR5 activity via desensitization (p < 0.01). In addition, we find altered protein-protein interaction (PPI) of mGluR5 with RGS4, norbin, Preso 1 and tamalin, which can also attenuate mGluR5 activity. We previously reported molecular underpinnings of GluN hypofunction (decreased GluN2 phosphorylation) and here we show those of reduced mGluR5 signaling in schizophrenia. We find that reduced GluN2 phosphorylation can be precipitated by attenuated mGluR5 activity and that increased mGluR5 phosphorylation can result from decreased GluN function, suggesting a reciprocal interplay between the two pathways in schizophrenia. Interestingly, the patient group showed decreased mGluR5-GluN association (p < 0.01), a mechanistic basis for the reciprocal facilitation. In sum, we present the first direct evidence for mGluR5 hypoactivity, propose a reciprocal interplay between GluN and mGluR5 pathways as integral to glutamatergic dysregulation and suggest protein-protein interactions in mGluR5-GluN complexes as potential targets for intervention in schizophrenia.
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Affiliation(s)
- Hoau-Yan Wang
- Department of Physiology, Pharmacology and Neuroscience, City University of New York School of Medicine, New York, NY 10031,Department of Biology and Neuroscience, Graduate School of the City University of New York, NY 10016
| | - Mathew L. MacDonald
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104-3403
| | - Karin E. Borgmann-Winter
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104-3403,Department of Child and Adolescent Psychiatry and Behavioral Sciences, Children’s Hospital of Philadelphia, Philadelphia, PA 19104
| | - Anamika Banerjee
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104-3403
| | - Patrick Sleiman
- The Center for Applied Genomics, The Children’s Hospital of Philadelphia, and Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA, 19104
| | - Andrew Tom
- Department of Physiology, Pharmacology and Neuroscience, City University of New York School of Medicine, New York, NY 10031
| | - Amber Khan
- Department of Physiology, Pharmacology and Neuroscience, City University of New York School of Medicine, New York, NY 10031,Department of Biology and Neuroscience, Graduate School of the City University of New York, NY 10016
| | - Kuo-Chieh Lee
- Department of Physiology, Pharmacology and Neuroscience, City University of New York School of Medicine, New York, NY 10031
| | - Panos Roussos
- Department of Psychiatry, Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Steven J. Siegel
- Department of Psychiatry and the Behavioral Sciences, University of Southern California, Los Angeles, CA, 90007
| | - Scott E Hemby
- Department of Basic Pharmaceutical Sciences, High Point University, High Point, NC, 27106
| | - Warren B. Bilker
- Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Raquel E. Gur
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104-3403
| | - Chang-Gyu Hahn
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, 19104-3403, USA.
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Akkus F, Treyer V, Ametamey SM, Johayem A, Buck A, Hasler G. Metabotropic glutamate receptor 5 neuroimaging in schizophrenia. Schizophr Res 2017; 183:95-101. [PMID: 27847228 DOI: 10.1016/j.schres.2016.11.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 10/20/2016] [Accepted: 11/09/2016] [Indexed: 11/29/2022]
Abstract
The metabotropic glutamate receptor 5 (mGluR5) is a promising drug target for the treatment of schizophrenia. In this study, we compared mGluR5 distribution volume ration (DVR) in subjects with schizophrenia and healthy controls. Given our previous findings, we matched samples for gender, age, and smoking status. Binding to mGluR5 was determined using positron emission tomography and [11C]ABP688, which binds to an allosteric site with high selectivity. DVR in the 15 individuals with schizophrenia did not differ from that of the 15 controls. In both groups, smoking was associated with marked global reductions in mGluR5 availability (on average 23.8%). In nonsmoking subjects with schizophrenia, there was a positive correlation between mGluR5 DVR in the medial orbitofrontal cortex and the use of antipsychotic drugs (r=0.9, p=0.019). Because antipsychotic drugs such as clozapine appeared to have indirect effects on mGluR5 signaling, our findings may be clinically relevant. They also provide promising leads for elucidating the high comorbidity between schizophrenia and tobacco addiction. Low mGluR5 DVR in smokers my represent a risk factor for schizophrenia. Alternatively, smoking may counteract the potential upregulation of mGluR5 by antipsychotic drugs.
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Affiliation(s)
- Funda Akkus
- Psychiatric University Hospital, University of Bern, 3000 Bern 60, Switzerland
| | - Valerie Treyer
- PET Center, Division of Nuclear Medicine, University Hospital, 8091 Zurich, Switzerland
| | - Simon M Ametamey
- Center for Radiopharmaceutical Science of ETH, PSI, and USZ, Department of Chemistry and Applied Biosciences of ETH, 8093 Zurich, Switzerland
| | - Anass Johayem
- PET Center, Division of Nuclear Medicine, University Hospital, 8091 Zurich, Switzerland
| | - Alfred Buck
- PET Center, Division of Nuclear Medicine, University Hospital, 8091 Zurich, Switzerland
| | - Gregor Hasler
- Psychiatric University Hospital, University of Bern, 3000 Bern 60, Switzerland.
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García-Bea A, Walker MA, Hyde TM, Kleinman JE, Harrison PJ, Lane TA. Metabotropic glutamate receptor 3 (mGlu3; mGluR3; GRM3) in schizophrenia: Antibody characterisation and a semi-quantitative western blot study. Schizophr Res 2016; 177:18-27. [PMID: 27130562 PMCID: PMC5145804 DOI: 10.1016/j.schres.2016.04.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 04/06/2016] [Accepted: 04/11/2016] [Indexed: 01/08/2023]
Abstract
BACKGROUND Metabotropic glutamate receptor 3 (mGlu3, mGluR3), encoded by GRM3, is a risk gene for schizophrenia and a therapeutic target. It is unclear whether expression of the receptor is altered in the disorder or related to GRM3 risk genotype. Antibodies used to date to assess mGlu3 in schizophrenia have not been well validated. OBJECTIVE To characterise six commercially available anti-mGlu3 antibodies for use in human brain, and then conduct a semi-quantitative study of mGlu3 immunoreactivity in schizophrenia. METHODS Antibodies tested using Grm3-/- and Grm2-/-/3-/- mice and transfected HEK293T/17 cells. Western blotting on membrane protein isolated from superior temporal cortex of 70 patients with schizophrenia and 87 healthy comparison subjects, genotyped for GRM3 SNP rs10234440. RESULTS One (out of six) anti-mGlu3 antibodies was fully validated, a C-terminal antibody which detected monomeric (~100kDa) and dimeric (~200kDa) mGlu3. A second, N-terminal, antibody detected the 200kDa band but also produced non-specific bands. Using the C-terminal antibody for western blotting in human brain, mGlu3 immunoreactivity was found to decline with age, and was affected by pH and post mortem interval. There were no differences in monomeric or dimeric mGlu3 immunoreactivity in schizophrenia or in relation to GRM3 genotype. The antibody was not suitable for immunohistochemistry. INTERPRETATION These data highlight the value of knockout mouse tissue for antibody validation, and the need for careful antibody characterisation. The schizophrenia data show that involvement of GRM3 in the disorder and its genetic risk architecture is not reflected in total membrane mGlu3 immunoreactivity in superior temporal cortex.
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Affiliation(s)
| | - Mary A Walker
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom
| | - Thomas M Hyde
- Lieber Institute for Brain Development, Baltimore, USA; Department of Neurology, Johns Hopkins School of Medicine, Baltimore, USA; Department of Psychiatry & Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, USA
| | | | - Paul J Harrison
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom; Oxford Health NHS Foundation Trust, Warneford Hospital, Oxford, United Kingdom
| | - Tracy A Lane
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom.
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5-HT2A and mGlu2/3 receptor interactions: on their relevance to cognitive function and psychosis. Behav Pharmacol 2016; 27:1-11. [PMID: 26292187 DOI: 10.1097/fbp.0000000000000183] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Serotonin [5-hydroxytryptamine (5-HT)] and glutamate have both been implicated in the pathophysiology of neuropsychiatric disorders but also in the mechanism of antipsychotic and hallucinogenic drug actions. Furthermore, close antagonistic interactions between 5-HT2A and metabotropic glutamate (mGlu)2/3 receptors have been established over the last decades on the basis of numerous electrophysiological, biochemical, and behavioral studies. Besides synaptic mechanisms, more recent findings suggested that heterodimeric 5-HT2A-mGlu2 receptor complexes in the prefrontal cortex may account for the functional crosstalk between these two receptor subtypes. In this review, we focus on in-vitro and in-vivo studies documenting the important relationship between 5-HT2A and mGlu2/3 receptors, with relevance to both normal behavioral function and psychosis.
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Muguruza C, Meana JJ, Callado LF. Group II Metabotropic Glutamate Receptors as Targets for Novel Antipsychotic Drugs. Front Pharmacol 2016; 7:130. [PMID: 27242534 PMCID: PMC4873505 DOI: 10.3389/fphar.2016.00130] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/05/2016] [Indexed: 11/13/2022] Open
Abstract
Schizophrenia is a chronic psychiatric disorder which substantially impairs patients' quality of life. Despite the extensive research in this field, the pathophysiology and etiology of schizophrenia remain unknown. Different neurotransmitter systems and functional networks have been found to be affected in the brain of patients with schizophrenia. In this context, postmortem brain studies as well as genetic assays have suggested alterations in Group II metabotropic glutamate receptors (mGluRs) in schizophrenia. Despite many years of drug research, several needs in the treatment of schizophrenia have not been addressed sufficiently. In fact, only 5-10% of patients with schizophrenia successfully achieve a full recovery after treatment. In recent years mGluRs have turned up as novel targets for the design of new antipsychotic medications for schizophrenia. Concretely, Group II mGluRs are of particular interest due to their regulatory role in neurotransmission modulating glutamatergic activity in brain synapses. Preclinical studies have demonstrated that orthosteric Group II mGluR agonists exhibit antipsychotic-like properties in animal models of schizophrenia. However, when these compounds have been tested in human clinical studies with schizophrenic patients results have been inconclusive. Nevertheless, it has been recently suggested that this apparent lack of efficacy in schizophrenic patients may be related to previous exposure to atypical antipsychotics. Moreover, the role of the functional heterocomplex formed by 5-HT2A and mGlu2 receptors in the clinical response to Group II mGluR agonists is currently under study.
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Affiliation(s)
- Carolina Muguruza
- Department of Pharmacology, University of the Basque Country, UPV/EHULeioa, Spain
- Centro de Investigación Biomédica en Red de Salud MentalMadrid, Spain
| | - J. Javier Meana
- Department of Pharmacology, University of the Basque Country, UPV/EHULeioa, Spain
- Centro de Investigación Biomédica en Red de Salud MentalMadrid, Spain
| | - Luis F. Callado
- Department of Pharmacology, University of the Basque Country, UPV/EHULeioa, Spain
- Centro de Investigación Biomédica en Red de Salud MentalMadrid, Spain
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Metabotropic glutamate receptor 5 – a promising target in drug development and neuroimaging. Eur J Nucl Med Mol Imaging 2016; 43:1151-70. [DOI: 10.1007/s00259-015-3301-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 12/22/2015] [Indexed: 10/22/2022]
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Shifting towards a model of mGluR5 dysregulation in schizophrenia: Consequences for future schizophrenia treatment. Neuropharmacology 2015; 115:73-91. [PMID: 26349010 DOI: 10.1016/j.neuropharm.2015.08.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 08/02/2015] [Accepted: 08/03/2015] [Indexed: 12/22/2022]
Abstract
Metabotropic glutamate receptor subtype 5 (mGluR5), encoded by the GRM5 gene, represents a compelling novel drug target for the treatment of schizophrenia. mGluR5 is a postsynaptic G-protein coupled glutamate receptor strongly linked with several critical cellular processes that are reported to be disrupted in schizophrenia. Accordingly, mGluR5 positive allosteric modulators show encouraging therapeutic potential in preclinical schizophrenia models, particularly for the treatment of cognitive dysfunctions against which currently available therapeutics are largely ineffective. More work is required to support the progression of mGluR5-targeting drugs into the clinic for schizophrenia treatment, although some obstacles may be overcome by comprehensively understanding how mGluR5 itself is involved in the neurobiology of the disorder. Several processes that are necessary for the regulation of mGluR5 activity have been identified, but not examined, in the context of schizophrenia. These processes include protein-protein interactions, dimerisation, subcellular trafficking, the impact of genetic variability or mutations on protein function, as well as epigenetic, post-transcriptional and post-translational processes. It is essential to understand these aspects of mGluR5 to determine whether they are affected in schizophrenia pathology, and to assess the consequences of mGluR5 dysfunction for the future use of mGluR5-based drugs. Here, we summarise the known processes that regulate mGluR5 and those that have already been studied in schizophrenia, and discuss the consequences of this dysregulation for current mGluR5 pharmacological strategies. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.
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Fatemi SH, Folsom TD. GABA receptor subunit distribution and FMRP-mGluR5 signaling abnormalities in the cerebellum of subjects with schizophrenia, mood disorders, and autism. Schizophr Res 2015; 167:42-56. [PMID: 25432637 PMCID: PMC5301472 DOI: 10.1016/j.schres.2014.10.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 12/24/2022]
Abstract
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABAergic receptor abnormalities have been documented in several major psychiatric disorders including schizophrenia, mood disorders, and autism. Abnormal expression of mRNA and protein for multiple GABA receptors has also been observed in multiple brain regions leading to alterations in the balance between excitatory/inhibitory signaling in the brain with potential profound consequences for normal cognition and maintenance of mood and perception. Altered expression of GABAA receptor subunits has been documented in fragile X mental retardation 1 (FMR1) knockout mice, suggesting that loss of its protein product, fragile X mental retardation protein (FMRP), impacts GABAA subunit expression. Recent postmortem studies from our laboratory have shown reduced expression of FMRP in the brains of subjects with schizophrenia, bipolar disorder, major depression, and autism. FMRP acts as a translational repressor and, under normal conditions, inhibits metabotropic glutamate receptor 5 (mGluR5)-mediated signaling. In fragile X syndrome (FXS), the absence of FMRP is hypothesized to lead to unregulated mGluR5 signaling, ultimately resulting in the behavioral and intellectual impairments associated with this disorder. Our laboratory has identified changes in mGluR5 expression in autism, schizophrenia, and mood disorders. In the current review article, we discuss our postmortem data on GABA receptors, FMRP, and mGluR5 levels and compare our results with other laboratories. Finally, we discuss the interactions between these molecules and the potential for new therapeutic interventions that target these interconnected signaling systems.
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Affiliation(s)
- S Hossein Fatemi
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota Medical School, 321 Church St. SE, Minneapolis, MN 55455, USA.
| | - Timothy D Folsom
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA.
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In the grey zone between epilepsy and schizophrenia: alterations in group II metabotropic glutamate receptors. Acta Neurol Belg 2015; 115:221-32. [PMID: 25539775 DOI: 10.1007/s13760-014-0407-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 12/05/2014] [Indexed: 01/09/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the brain. The glutamate system plays an important role in the formation of synapses during brain development and synaptic plasticity. Dysfunctions in glutamate regulation may lead to hyperexcitatory neuronal networks and neurotoxicity. Glutamate excess is possibly of great importance in the pathophysiology of several neurological and psychiatric disorders such as epilepsy and schizophrenia. Interestingly, cross talk between these disorders has been well documented: psychiatric comorbidities are frequent in epilepsy and temporal lobe epilepsy is one of the highest risk factors for developing psychosis. Therefore, dysfunctions in glutamatergic neurotransmission might constitute a common pathological mechanism. A major negative feedback system is regulated by the presynaptic group II metabotropic glutamate (mGlu) receptors including mGlu2/3 receptors. These receptors are predominantly localised extrasynaptically in basal ganglia and limbic structures. Hence, mGlu2/3 receptors are an interesting target for the treatment of disorders like epilepsy and schizophrenia. A dysfunction in the glutamate system may be associated with alterations in mGlu2/3 receptor expression. In this review, we describe the localization of mGlu2/3 receptors in the healthy brain of mice, rats and humans. Secondly, changes in mGlu2/3 receptor density of the brain regions affected in epilepsy and schizophrenia are summarised. Increased mGlu2/3 receptor density might represent a compensatory mechanism of the brain to regulate elevated glutamate levels, while reduced mGlu2/3 receptor density in some brain regions may further contribute to the aberrant hyperexcitability. Further research considering the mGlu2/3 receptor can contribute significantly to the understanding of the etiological and therapeutic role of group II mGlu receptor in epilepsy, epilepsy with psychosis and schizophrenia.
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12
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Ellaithy A, Younkin J, González-Maeso J, Logothetis DE. Positive allosteric modulators of metabotropic glutamate 2 receptors in schizophrenia treatment. Trends Neurosci 2015; 38:506-16. [PMID: 26148747 PMCID: PMC4530036 DOI: 10.1016/j.tins.2015.06.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 06/07/2015] [Accepted: 06/11/2015] [Indexed: 12/22/2022]
Abstract
The past two decades have witnessed a rise in the 'NMDA receptor hypofunction' hypothesis for schizophrenia, a devastating disorder that affects around 1% of the population worldwide. A variety of presynaptic, postsynaptic, and regulatory proteins involved in glutamatergic signaling have thus been proposed as potential therapeutic targets. This review focuses on positive allosteric modulation of metabotropic glutamate 2 receptors (mGlu2Rs) and discusses how recent preclinical epigenetic data may provide a molecular explanation for the discrepant results of clinical studies, further stimulating the field to exploit the promise of mGlu2R as a target for schizophrenia treatment.
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Affiliation(s)
- Amr Ellaithy
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Jason Younkin
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
| | - Javier González-Maeso
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA; Departments of Psychiatry and Neurology, and The Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
| | - Diomedes E Logothetis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA.
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13
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The role of the thalamus in schizophrenia from a neuroimaging perspective. Neurosci Biobehav Rev 2015; 54:57-75. [DOI: 10.1016/j.neubiorev.2015.01.013] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 12/19/2014] [Accepted: 01/12/2015] [Indexed: 02/06/2023]
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14
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Matosin N, Fernandez-Enright F, Frank E, Deng C, Wong J, Huang XF, Newell KA. Metabotropic glutamate receptor mGluR2/3 and mGluR5 binding in the anterior cingulate cortex in psychotic and nonpsychotic depression, bipolar disorder and schizophrenia: implications for novel mGluR-based therapeutics. J Psychiatry Neurosci 2014; 39:407-16. [PMID: 24949866 PMCID: PMC4214875 DOI: 10.1503/jpn.130242] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Metabotropic glutamate receptors 2/3 (mGluR2/3) and 5 (mGluR5) are novel therapeutic targets for major depression (MD), bipolar disorder (BD) and schizophrenia. We aimed to determine whether mGluR2/3 and mGluR5 binding in the anterior cingulate cortex (ACC), a brain region essential for the regulation of mood, cognition and emotion, were differentially altered in these pathologies. METHODS Using postmortem human brains derived from 2 cohorts, [(3)H]LY341495 binding to mGluR2/3 and [(3)H]MPEP binding to mGluR5 were measured by receptor autoradiography in the ACC. The first cohort comprised samples from individuals who had MD with psychosis (MDP), MD without psychosis (MDNP) and matched controls (n = 11-12 per group). The second cohort comprised samples from individuals who had MDNP, BD, schizophrenia and matched controls (n = 15 per group). RESULTS No differences in mGluR2/3 or mGluR5 binding were observed in the MDP, MDNP, BD or schizophrenia groups compared with the control group (all p > 0.05). Importantly, there were also no differences in binding densities between the psychiatric disorders (p > 0.05). We did, however, observe age-related effects, with consistent negative associations between mGluR2/3 and age in the control group (r < -0.575, p < 0.025) and the psychotic disorder groups (MDP and schizophrenia: r = -0.765 to -0.515, p < 0.05), but not in the mood disorder groups (MDNP, BD). LIMITATIONS Replication in larger independent cohorts and medication-naive individuals would strengthen these findings. CONCLUSION Our findings suggest that mGluRs are unaltered in the ACC; however, the presence of altered receptor function cannot be discounted and requires further investigation. Taken together with previous studies, which report differential changes in mGluR2, 3 and 5 across these disorders, we suggest mGluRs may be affected in a brain region-specific manner.
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Affiliation(s)
| | | | | | | | | | | | - Kelly A. Newell
- Correspondence to: K.A. Newell, University of Wollongong, Northfields Ave., Wollongong, NSW 2522, Australia;
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Hu W, MacDonald ML, Elswick DE, Sweet RA. The glutamate hypothesis of schizophrenia: evidence from human brain tissue studies. Ann N Y Acad Sci 2014; 1338:38-57. [PMID: 25315318 DOI: 10.1111/nyas.12547] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A number of studies have indicated that antagonists of the N-methyl-d-aspartate subtypes of glutamate receptors can cause schizophrenia-like symptoms in healthy individuals and exacerbate symptoms in individuals with schizophrenia. These findings have led to the glutamate hypothesis of schizophrenia. Here we review the evidence for this hypothesis in postmortem studies of brain tissue from individuals affected by schizophrenia, summarizing studies of glutamate neuron morphology, of expression of glutamate receptors and transporters, and of the synthesizing and metabolizing enzymes for glutamate and its co-agonists. We found consistent evidence of morphological alterations of dendrites of glutamatergic neurons in the cerebral cortex of subjects with schizophrenia and of reduced levels of the axon bouton marker synaptophysin. There were no consistent alterations of mRNA expression of glutamate receptors, although there has been limited study of the corresponding proteins. Studies of the glutamate metabolic pathway have been limited, although there is some evidence that excitatory amino acid transporter-2, glutamine synthetase, and glutaminase have altered expression in schizophrenia. Future studies would benefit from additional direct examination of glutamatergic proteins. Further advances, such as selective testing of synaptic microdomains, cortical layers, and neuronal subtypes, may also be required to elucidate the nature of glutamate signaling impairments in schizophrenia.
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Affiliation(s)
- Wei Hu
- Department of Behavioral Medicine and Psychiatry, West Virginia University Health Sciences Center, Morgantown, West Virginia
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Iasevoli F, Tomasetti C, Buonaguro EF, de Bartolomeis A. The glutamatergic aspects of schizophrenia molecular pathophysiology: role of the postsynaptic density, and implications for treatment. Curr Neuropharmacol 2014; 12:219-38. [PMID: 24851087 PMCID: PMC4023453 DOI: 10.2174/1570159x12666140324183406] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/14/2014] [Accepted: 03/14/2014] [Indexed: 01/23/2023] Open
Abstract
Schizophrenia is one of the most debilitating psychiatric diseases with a lifetime prevalence of approximately
1%. Although the specific molecular underpinnings of schizophrenia are still unknown, evidence has long linked its
pathophysiology to postsynaptic abnormalities.
The postsynaptic density (PSD) is among the molecular structures suggested to be potentially involved in schizophrenia.
More specifically, the PSD is an electron-dense thickening of glutamatergic synapses, including ionotropic and
metabotropic glutamate receptors, cytoskeletal and scaffolding proteins, and adhesion and signaling molecules. Being
implicated in the postsynaptic signaling of multiple neurotransmitter systems, mostly dopamine and glutamate, the PSD
constitutes an ideal candidate for studying dopamine-glutamate disturbances in schizophrenia. Recent evidence suggests
that some PSD proteins, such as PSD-95, Shank, and Homer are implicated in severe behavioral disorders, including
schizophrenia. These findings, further corroborated by genetic and animal studies of schizophrenia, offer new insights for
the development of pharmacological strategies able to overcome the limitations in terms of efficacy and side effects of
current schizophrenia treatment. Indeed, PSD proteins are now being considered as potential molecular targets against this
devastating illness.
The current paper reviews the most recent hypotheses on the molecular mechanisms underlying schizophrenia
pathophysiology. First, we review glutamatergic dysfunctions in schizophrenia and we provide an update on postsynaptic
molecules involvement in schizophrenia pathophysiology by addressing both human and animal studies. Finally, the
possibility that PSD proteins may represent potential targets for new molecular interventions in psychosis will be
discussed.
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Affiliation(s)
- Felice Iasevoli
- Department of Neuroscience, Reproductive and Odontostomatological Sciences - University "Federico II", Naples, Italy
| | - Carmine Tomasetti
- Department of Neuroscience, Reproductive and Odontostomatological Sciences - University "Federico II", Naples, Italy
| | - Elisabetta F Buonaguro
- Department of Neuroscience, Reproductive and Odontostomatological Sciences - University "Federico II", Naples, Italy
| | - Andrea de Bartolomeis
- Department of Neuroscience, Reproductive and Odontostomatological Sciences - University "Federico II", Naples, Italy
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Rubio MD, Drummond JB, Meador-Woodruff JH. Glutamate receptor abnormalities in schizophrenia: implications for innovative treatments. Biomol Ther (Seoul) 2014; 20:1-18. [PMID: 24116269 PMCID: PMC3792192 DOI: 10.4062/biomolther.2012.20.1.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 11/25/2011] [Indexed: 01/18/2023] Open
Abstract
Schizophrenia is a devastating psychiatric illness that afflicts 1% of the population worldwide, resulting in substantial impact to patients, their families, and health care delivery systems. For many years, schizophrenia has been felt to be associated with dysregulated dopaminergic neurotransmission as a key feature of the pathophysiology of the illness. Although numerous studies point to dopaminergic abnormalities in schizophrenia, dopamine dysfunction cannot completely account for all of the symptoms seen in schizophrenia, and dopamine-based treatments are often inadequate and can be associated with serious side effects. More recently, converging lines of evidence have suggested that there are abnormalities of glutamate transmission in schizophrenia. Glutamatergic neurotransmission involves numerous molecules that facilitate glutamate release, receptor activation, glutamate reuptake, and other synaptic activities. Evidence for glutamatergic abnormalities in schizophrenia primarily has implicated the NMDA and AMPA subtypes of the glutamate receptor. The expression of these receptors and other molecules associated with glutamate neurotransmission has been systematically studied in the brain in schizophrenia. These studies have generally revealed region- and molecule-specific changes in glutamate receptor transcript and protein expression in this illness. Given that glutamatergic neurotransmission has been implicated in the pathophysiology of schizophrenia, recent drug development efforts have targeted the glutamate system. Much effort to date has focused on modulation of the NMDA receptor, although more recently other glutamate receptors and transporters have been the targets of drug development. These efforts have been promising thus far, and ongoing efforts to develop additional drugs that modulate glutamatergic neurotransmission are underway that may hold the potential for novel classes of more effective treatments for this serious psychiatric illness.
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Affiliation(s)
- Maria D Rubio
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294-0021, USA
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Newell KA, Matosin N. Rethinking metabotropic glutamate receptor 5 pathological findings in psychiatric disorders: implications for the future of novel therapeutics. BMC Psychiatry 2014; 14:23. [PMID: 24472577 PMCID: PMC3907147 DOI: 10.1186/1471-244x-14-23] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 01/21/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Pharmacological modulation of metabotropic glutamate receptor 5 (mGluR5) is of marked interest as a novel therapeutic mechanism to treat schizophrenia and major depression. However, the status of mGluR5 in the pathophysiology of these disorders remains unknown. DISCUSSION The majority of studies in the schizophrenia post-mortem brain indicate that total mGluR5 expression is unaltered. However, close examination of the literature suggests that these findings are superficial, and in actuality, a number of critical factors have not yet been considered; alterations may be highly dependent on brain region, neuronal population or molecular organisation in specific cellular compartments. A number of genetic knockout studies (mGluR5, Norbin, Homer1 etc.) continue to lend support to a role of mGluR5 in the pathology of schizophrenia, providing impetus to explore the regulation of mGluR5 beyond total mGluR5 protein and mRNA levels. With regards to major depression, preliminary evidence to date shows a reduction in total mGluR5 protein and mRNA levels; however, as in schizophrenia, there are no studies examining mGluR5 function or regulation in the pathological state. A comprehensive understanding of mGluR5 regulation in major depression, particularly in comparison to schizophrenia, is crucial as this has extensive implications for mGluR5 targeting novel therapeutics, especially considering that opposing modulation of mGluR5 is of therapeutic interest for these two disorders. SUMMARY Despite the complexities, examinations of post-mortem human brain provide valuable insights into the pathologies of these inherently human disorders. It is important, especially with regards to the identification of novel therapeutic drug targets, to have an in depth understanding of the pathophysiologies of these disorders. We posit that brain region- and cell type-specific alterations exist in mGluR5 in schizophrenia and depression, with evidence pointing towards altered regulation of this receptor in psychiatric pathology. We consider the implications of these alterations, as well as the distinction between schizophrenia and depression, in the context of novel mGluR5 based therapeutics.
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Affiliation(s)
- Kelly A Newell
- Centre for Translational Neuroscience, Faculty of Science, Medicine and Health and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia.
| | - Natalie Matosin
- Centre for Translational Neuroscience, Faculty of Science, Medicine and Health and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia,Schizophrenia Research Institute, Darlinghurst, NSW 2010, Australia
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mRNA and protein expression for novel GABAA receptors θ and ρ2 are altered in schizophrenia and mood disorders; relevance to FMRP-mGluR5 signaling pathway. Transl Psychiatry 2013; 3:e271. [PMID: 23778581 PMCID: PMC3693405 DOI: 10.1038/tp.2013.46] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) is an RNA-binding protein that targets ∼5% of all mRNAs expressed in the brain. Previous work by our laboratory demonstrated significantly lower protein levels for FMRP in lateral cerebella of subjects with schizophrenia, bipolar disorder and major depression when compared with controls. Absence of FMRP expression in animal models of fragile X syndrome (FXS) has been shown to reduce expression of gamma-aminobutyric acid A (GABAA) receptor mRNAs. Previous work by our laboratory has found reduced expression of FMRP, as well as multiple GABAA and GABAB receptor subunits in subjects with autism. Less is known about levels for GABAA subunit protein expression in brains of subjects with schizophrenia and mood disorders. In the current study, we have expanded our previous studies to examine the protein and mRNA expression of two novel GABAA receptors, theta (GABRθ) and rho 2 (GABRρ2) as well as FMRP, and metabotropic glutamate receptor 5 (mGluR5) in lateral cerebella of subjects with schizophrenia, bipolar disorder, major depression and healthy controls, and in superior frontal cortex (Brodmann Area 9 (BA9)) of subjects with schizophrenia, bipolar disorder and healthy controls. We observed multiple statistically significant mRNA and protein changes in levels of GABRθ, GABRρ2, mGluR5 and FMRP molecules including concordant reductions in mRNA and proteins for GABRθ and mGluR5 in lateral cerebella of subjects with schizophrenia; for increased mRNA and protein for GABRρ2 in lateral cerebella of subjects with bipolar disorder; and for reduced mRNA and protein for mGluR5 in BA9 of subjects with bipolar disorder. There were no significant effects of confounds on any of the results.
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20
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Matosin N, Frank E, Deng C, Huang XF, Newell KA. Metabotropic glutamate receptor 5 binding and protein expression in schizophrenia and following antipsychotic drug treatment. Schizophr Res 2013; 146:170-6. [PMID: 23462049 DOI: 10.1016/j.schres.2013.01.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 01/03/2013] [Accepted: 01/10/2013] [Indexed: 11/17/2022]
Abstract
Metabotropic glutamate receptor 5 (mGluR5) has been identified as a potential therapeutic target for schizophrenia, primarily due to its ability to indirectly modulate glutamatergic signalling through the NMDA receptor (NMDAR). Despite its potential, molecular studies characterising mGluR5 in schizophrenia are limited. We therefore aimed to determine if the mGluR5 binding site or protein levels were altered in schizophrenia or by current antipsychotics. Using in-situ radioligand binding and immunoblot, we measured [(3)H]MPEP binding to mGluR5 and mGluR5 protein density in the post-mortem dorsolateral prefrontal cortex (DLPFC; BA46) of 37 schizophrenia and 37 matched control subjects. Subsequently, we measured [(3)H]MPEP binding in rat brains following typical (haloperidol) or atypical (olanzapine) antipsychotic treatment (n = 6/group). Subjects with schizophrenia showed no significant alteration in mGluR5 binding density or mGluR5 protein levels. Furthermore, mGluR5 binding in the rat cortex, thalamus, hippocampus and striatum was unaltered by short-, medium- and long-term antipsychotic treatment. Our data suggests that there are no alterations in mGluR5 in schizophrenia subjects. The lack of alteration in mGluR5 binding and protein in schizophrenia is advantageous because its ability to modulate the NMDAR is potentially unhindered, thereby supporting the development of novel antipsychotic agents that work through the mGluR5/NMDAR complex.
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Affiliation(s)
- Natalie Matosin
- Centre for Translational Neuroscience, Illawarra Health and Medical Research Institute, School of Health Sciences, University of Wollongong, NSW 2522, Australia.
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21
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Matosin N, Newell KA. Metabotropic glutamate receptor 5 in the pathology and treatment of schizophrenia. Neurosci Biobehav Rev 2012; 37:256-68. [PMID: 23253944 DOI: 10.1016/j.neubiorev.2012.12.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/27/2012] [Accepted: 12/09/2012] [Indexed: 02/07/2023]
Abstract
Metabotropic glutamate receptor 5 (mGluR5) potentiates the NMDA receptor (NMDAR) in brain regions implicated in schizophrenia, making it a viable therapeutic target for the treatment of this disorder. mGluR5 positive allosteric modulators may represent a valuable novel strategy for schizophrenia treatment, given the favourable profile of effects in preclinical paradigms. However it remains unclear whether mGluR5 also plays a causal or epiphenomenal role in NMDAR dysfunction in schizophrenia. Animal and cellular data suggest involvement of mGluR5, whilst post-mortem human studies remain inconclusive. This review will explore the molecular, animal and human data to support and refute the involvement of mGluR5 in the pathology of schizophrenia. Furthermore, this review will discuss the potential of mGluR5 modulators in the therapy of schizophrenia as well as aspects of mGluR5 that require further characterisation.
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Affiliation(s)
- Natalie Matosin
- Centre for Translational Neuroscience, Illawarra Health and Medical Research Institute, School of Health Sciences, University of Wollongong, NSW 2522, Australia
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Kordi-Tamandani DM, Dahmardeh N, Torkamanzehi A. Evaluation of hypermethylation and expression pattern of GMR2, GMR5, GMR8, and GRIA3 in patients with schizophrenia. Gene 2012; 515:163-6. [PMID: 23149219 DOI: 10.1016/j.gene.2012.10.075] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Revised: 10/11/2012] [Accepted: 10/30/2012] [Indexed: 11/26/2022]
Abstract
UNLABELLED Emerging evidence suggests a role of dysfunction of glutamatergic neurotransmission and its receptors in the pathophysiology of schizophrenia (SCZ). This study evaluated whether the promoter hypermethylation and RNA expression pattern of GMR2 (glutamate metabotropic receptor), GMR5, GMR8, and GRIA3 (glutamate receptor, ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) are associated with the risk of schizophrenia between schizophrenia patients and healthy controls. MATERIALS AND METHODS Methylation-specific polymerase chain reaction (MS-PCR) was used to estimate the promoter hypermethylation of GMR2, GMR5, GMR8, and GRIA3 genes on 81 isolated genomic DNA samples from the peripheral blood of individuals with schizophrenia and 71 healthy control subjects. In addition, real-time reverse transcription-PCR was used to estimate mRNA levels in 34 blood samples of healthy controls and cases. RESULTS The methylation of GRM2 and GRM5 greatly decreased the risk of schizophrenia in comparison to the reference unmethylated pattern [OR=0.38, 95% CI; 0.144-1.035, p=0.05; OR=0.06, 95% CI; 0.007-0.54.10, p=0.01], respectively. The methylation of GRIA3 highly increased the risk of schizophrenia, but non-significant (OR=2.3, 95% CI; 0.51-10.42). The outcomes of the expression analysis revealed a statistically significant difference between the cases (n=17) and healthy controls (n=17) regarding the relative gene expression of GRM2, GRM5, and GRIA3 (p=0.0001). CONCLUSION To the best of our knowledge, this is the first evidence showing that the promoter methylation of the GMR2 and GMR5 genes greatly decreased the risk of schizophrenia, and the expression level of the GRM2, GRM5, and GRIA3 genes increased significantly in patients in comparison to healthy controls. These outcomes suggest that there is a need for more attention to be paid to the effect of epigenetic variations in the development of SCZ in further investigations.
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Herman EJ, Bubser M, Conn PJ, Jones CK. Metabotropic glutamate receptors for new treatments in schizophrenia. Handb Exp Pharmacol 2012:297-365. [PMID: 23027420 DOI: 10.1007/978-3-642-25758-2_11] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Metabotropic glutamate receptors (mGluRs) represent exciting targets for the development of novel therapeutic agents for schizophrenia. Recent studies indicate that selective activation of specific mGluR subtypes may provide potential benefits for not only the positive symptoms, but also the negative symptoms and cognitive impairments observed in individuals with schizophrenia. Although optimization of traditional orthosteric agonists may still offer a feasible approach for the activation of mGluRs, important progress has been made in the discovery of novel subtype-selective allosteric ligands, including positive allosteric modulators (PAMs) of mGluR2 and mGluR5. These allosteric mGluR ligands have improved properties for clinical development and have served as key preclinical tools for a more in-depth understanding of the potential roles of these different mGluR subtypes for the treatment of schizophrenia.
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Affiliation(s)
- E J Herman
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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Sodhi MS, Simmons M, McCullumsmith R, Haroutunian V, Meador-Woodruff JH. Glutamatergic gene expression is specifically reduced in thalamocortical projecting relay neurons in schizophrenia. Biol Psychiatry 2011; 70:646-54. [PMID: 21549355 PMCID: PMC3176961 DOI: 10.1016/j.biopsych.2011.02.022] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 01/28/2011] [Accepted: 02/22/2011] [Indexed: 11/28/2022]
Abstract
BACKGROUND Impairment of glutamate neurons that relay sensory and cognitive information from the medial dorsal thalamus to the dorsolateral prefrontal cortex and other cortical regions may contribute to the pathophysiology of schizophrenia. In this study, we have assessed the cell-specific expression of glutamatergic transcripts in the medial dorsal thalamus. METHODS We used laser capture microdissection to harvest two populations of medial dorsal thalamic cells, one enriched with glutamatergic relay neurons and the other with gamma-aminobutyric acidergic neurons and astroglia, from postmortem brains of subjects with schizophrenia (n = 14) and a comparison group (n = 20). Quantitative polymerase chain reaction of extracted RNA was used to assay gene expression in the different cell populations. RESULTS The transcripts encoding the ionotropic glutamate receptor subunits NR2D, GluR3, GluR6, GluR7, and the intracellular proteins GRIP1 and SynGAP1 were significantly decreased in relay neurons but not in the mixed glial and interneuron population in schizophrenia. CONCLUSIONS Our data suggest that reduced ionotropic glutamatergic expression occurs selectively in neurons, which give rise to the cortical projections of the medial dorsal thalamus in schizophrenia, rather than in thalamic cells that function locally. Our findings indicate that glutamatergic innervation is dysfunctional in the circuitry between the medial dorsal thalamus and cortex.
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Affiliation(s)
- Monsheel S. Sodhi
- Dept. Psychiatry and Behavioral Neurobiology, UAB, 1720 7 Avenue Sth. Birmingham, Alabama 35294-0019, USA,Dept. Pharmacy Practice and Center for Pharmaceutical Biotechnology, College of Pharmacy, 900 S Ashland Ave, Chicago, Illinois 60607-4067, USA,Correspondence should be addressed to: Monsheel Sodhi Ph.D., 900 S. Ashland Ave. Chicago IL 60607-4067, USA, Tel: +1-312-355-5949, Fax: +1-312-413-9303,
| | - Micah Simmons
- Dept. Psychiatry and Behavioral Neurobiology, UAB, 1720 7 Avenue Sth. Birmingham, Alabama 35294-0019, USA
| | - Robert McCullumsmith
- Dept. Psychiatry and Behavioral Neurobiology, UAB, 1720 7 Avenue Sth. Birmingham, Alabama 35294-0019, USA
| | - Vahram Haroutunian
- Dept. Psychiatry, The Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, New York 10029-6574, USA
| | - James H. Meador-Woodruff
- Dept. Psychiatry and Behavioral Neurobiology, UAB, 1720 7 Avenue Sth. Birmingham, Alabama 35294-0019, USA
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Corti C, Xuereb JH, Crepaldi L, Corsi M, Michielin F, Ferraguti F. Altered levels of glutamatergic receptors and Na+/K+ ATPase-α1 in the prefrontal cortex of subjects with schizophrenia. Schizophr Res 2011; 128:7-14. [PMID: 21353485 DOI: 10.1016/j.schres.2011.01.021] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 01/24/2011] [Accepted: 01/28/2011] [Indexed: 12/31/2022]
Abstract
Evidence has accumulated over the past years that dysregulation of glutamatergic neurotransmission maybe implicated in the pathophysiology of schizophrenia. Glutamate acts on two major classes of receptors: ionotropic receptors, which are ligand-gated ion channels, and metabotropic receptors (mGluRs), coupled to heterotrimeric G-proteins. Although several pharmacological evidences point to abnormal glutamatergic transmission in schizophrenia, changes in the expression of glutamatergic receptors in the prefrontal cortex of patients with schizophrenia remains equivocal. In the present work, we have investigated glutamatergic neurotransmission in schizophrenia by assessing the expression in Brodmann Area 10 of mGluR5, the AMPA receptor subunits GluR1 and GluR2, and Na(+)/K(+) ATPase-α1, a potential modulator of glutamate uptake in the brain. Semiquantitative analysis of the expression of these proteins from postmortem brains revealed a particularly prominent reduction of GluR1 and GluR2 expression in patients with schizophrenia vs the control group. Conversely, we observed an up-regulation in the levels of Na(+)/K(+) ATPase-α1 expression. Finally, no change in the protein levels of mGluR5 was observed in schizophrenia. Our findings support and expand the hypothesis of glutamatergic dysfunction in prefrontal cortex in the pathophysiology of schizophrenia.
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Affiliation(s)
- Corrado Corti
- Dept. Biology, Psychiatry Centre of Excellence in Drug Discovery, GlaxoSmithKline Medicines Research Centre, Verona, Italy
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Krystal JH, Mathew SJ, D'Souza DC, Garakani A, Gunduz-Bruce H, Charney DS. Potential psychiatric applications of metabotropic glutamate receptor agonists and antagonists. CNS Drugs 2010; 24:669-93. [PMID: 20658799 DOI: 10.2165/11533230-000000000-00000] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Drugs acting at metabotropic glutamate receptors (mGluRs) are among the most promising agents under development for the treatment of psychiatric disorders. The research in this area is at a relatively early stage, as there are no drugs acting at mGluRs that have been approved for the treatment of any psychiatric disorder. However, in the areas of schizophrenia, anxiety disorders and mood disorders, research conducted in animal models appears to translate well into efficacy in human laboratory-based models of psychopathology and in preliminary clinical trials. Further, the genes coding for mGluRs are implicated in the risk for a growing number of psychiatric disorders. This review highlights the best studied mGluR strategies for psychiatry, based on human molecular genetics, studies in animal models and preliminary clinical trials. It describes the potential value of mGluR2 and mGluR5 agonists and positive allosteric modulators for the treatment of schizophrenia. It also reviews evidence that group II mGluR agonists and positive allosteric modulators as well as group I mGluR antagonists might also treat anxiety disorders and some forms of depression, while mGluR2 and group I mGluR antagonists (particularly mGluR5 antagonists) might have antidepressant properties. This review also links growing insights into the role of glutamate in the pathophysiology of these disorders to hypothesized mGluR-related treatment mechanisms.
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Affiliation(s)
- John H Krystal
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, USA.
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Lesage A, Steckler T. Metabotropic glutamate mGlu1 receptor stimulation and blockade: therapeutic opportunities in psychiatric illness. Eur J Pharmacol 2010; 639:2-16. [PMID: 20371230 DOI: 10.1016/j.ejphar.2009.12.043] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2009] [Revised: 12/15/2009] [Accepted: 12/18/2009] [Indexed: 12/26/2022]
Abstract
Metabotropic glutamate mGlu(1) receptors play a modulatory role in the nervous system. They enhance cell excitability, modulate synaptic neurotransmission and are involved in synaptic plasticity. During the last 10 years, several selective metabotropic glutamate mGlu(1) receptor competitive antagonists and potentiators have been discovered. These pharmacological tools, together with early and later work in metabotropic glutamate mGlu(1) receptor mutant mice have allowed studying the role of the receptor in various aspects of psychiatric illnesses such as anxiety, depression and schizophrenia. We here review the data on selective metabotropic glutamate mGlu(1) receptor antagonists in support of their potential as anxiolytic and antidepressant treatments. We propose a rationale for the development of metabotropic glutamate mGlu(1) receptor positive allosteric modulators for the treatment of schizophrenia. Potential side effects of blockade and activation of metabotropic glutamate mGlu(1) receptors are addressed, with special focus on the differential effects of metabotropic glutamate mGlu(1) receptor antagonists in cognition models with positive reinforcement versus those that use aversive learning procedures. Further development of negative allosteric modulators and more drug-like positive allosteric modulators will be required in order to decipher the therapeutic efficacy and safety margin of these compounds in the clinic.
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Affiliation(s)
- Anne Lesage
- Department of CNS-Neuroscience, Research and Early Development, Johnson and Johnson Research and Development, Turnhoutseweg 30, 2340 Beerse, Belgium.
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Moreno JL, Sealfon SC, González-Maeso J. Group II metabotropic glutamate receptors and schizophrenia. Cell Mol Life Sci 2009; 66:3777-85. [PMID: 19707855 PMCID: PMC2792875 DOI: 10.1007/s00018-009-0130-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 07/10/2009] [Accepted: 08/11/2009] [Indexed: 12/18/2022]
Abstract
Schizophrenia is one of the most common mental illnesses, with hereditary and environmental factors important for its etiology. All antipsychotics have in common a high affinity for monoaminergic receptors. Whereas hallucinations and delusions usually respond to typical (haloperidol-like) and atypical (clozapine-like) monoaminergic antipsychotics, their efficacy in improving negative symptoms and cognitive deficits remains inadequate. In addition, devastating side effects are a common characteristic of monoaminergic antipsychotics. Recent biochemical, preclinical and clinical findings support group II metabotropic glutamate receptors (mGluR2 and mGluR3) as a new approach to treat schizophrenia. This paper reviews the status of general knowledge of mGluR2 and mGluR3 in the psychopharmacology, genetics and neuropathology of schizophrenia.
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Affiliation(s)
- José L. Moreno
- Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029 USA
- Division of Basic Neuroscience, Mount Sinai School of Medicine, New York, NY 10029 USA
| | - Stuart C. Sealfon
- Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029 USA
- Center for Translational Systems Biology, Mount Sinai School of Medicine, New York, NY 10029 USA
| | - Javier González-Maeso
- Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029 USA
- Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029 USA
- Division of Basic Neuroscience, Mount Sinai School of Medicine, New York, NY 10029 USA
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29
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Expression of a GRM3 splice variant is increased in the dorsolateral prefrontal cortex of individuals carrying a schizophrenia risk SNP. Neuropsychopharmacology 2008; 33:2626-34. [PMID: 18256595 DOI: 10.1038/sj.npp.1301669] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Genetic variation in the metabotropic glutamate receptor 3 (GRM3, mGluR3) has been associated with schizophrenia, but the mechanism by which it confers risk is unknown. Previously, we reported the existence of a splice variant, GRM3Delta4, which has an exon 4 deletion and encodes a truncated form of the receptor that is expressed in brain. The aim of the present study was to determine whether expression of this splice variant is altered in individuals with schizophrenia and is affected by a risk genotype. We measured GRM3 and GRM3Delta4 transcripts in human dorsolateral prefrontal cortex (DLPFC) and hippocampus of the CBDB/NIMH collection ( approximately 70 controls, approximately 30 schizophrenia patients) and in the DLPFC of the Stanley Array Collection. Expression data of GRM3 mRNA in the DLPFC were inconsistent: GRM3 was increased in schizophrenia patients in the CBDB/NIMH collection, but not in the Stanley Array Collection. GRM3 expression did not change in the frontal cortex of rats treated chronically with haloperidol or clozapine. An exon 3 SNP previously associated with schizophrenia (rs2228595) predicted increased expression of the GRM3Delta4 splice variant. Our results suggest that rs2228595, or a neighboring SNP in linkage disequilibrium with it, may contribute to risk for schizophrenia by modulating GRM3 splicing.
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30
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Krivoy A, Fischel T, Weizman A. The possible involvement of metabotropic glutamate receptors in schizophrenia. Eur Neuropsychopharmacol 2008; 18:395-405. [PMID: 18063347 DOI: 10.1016/j.euroneuro.2007.11.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 09/16/2007] [Accepted: 11/07/2007] [Indexed: 02/02/2023]
Abstract
Glutamate disruption is thought to have a major role in schizophrenia brain processes, possibly involving NMDA hypofunction. The metabotropic glutamate receptors are distributed in brain regions related to schizophrenia and seem to affect glutamate release in a moderate way. Compounds modulating these receptors are being investigated in animal models of schizophrenia, in an attempt to discover new antipsychotics. This article reviews the current research data regarding the role of these receptors in schizophrenia animal models. It was found that more research was done on Group I and II metabotropic receptors while investigation of group III receptors is still trailing behind. Accumulating evidence shows that mGluR5 antagonists by themselves do not necessarily disrupt pre-pulse inhibition (PPI), but can exacerbate disruption of PPI caused by MK-801 and PCP, while positive modulation of this receptor has beneficial effects on these models of psychosis. Group II agonists are also showing beneficial effects in animal models. It seems that metabotropic glutamate receptor modulators could be developed into a novel treatment of schizophrenia by altering glutamate release, thus overcoming the putative NMDA hypofunction. Although the implications from these pre-clinical studies to human schizophrenia patients are premature, the data obtained with some compounds point to promising results for drug development. More studies, with agents active at other mGluRs in animal models and schizophrenia patients as well as with human subjects are needed in order to clarify the role of the metabotropic glutamate receptors in the pathophysiology and pharmacotherapy of schizophrenia.
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Affiliation(s)
- Amir Krivoy
- Geha Mental Health Center, Petach-Tikva, Israel.
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31
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Harrison PJ, Lyon L, Sartorius LJ, Burnet PWJ, Lane TA. The group II metabotropic glutamate receptor 3 (mGluR3, mGlu3, GRM3): expression, function and involvement in schizophrenia. J Psychopharmacol 2008; 22:308-22. [PMID: 18541626 DOI: 10.1177/0269881108089818] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Group II metabotropic glutamate receptors (mGluRs) comprise mGluR2 (mGlu2; encoded by GRM2) and mGluR3 (mGlu3; encoded by GRM3) and modulate glutamate neurotransmission and synaptic plasticity. Here we review the expression and function of mGluR3 and its involvement in schizophrenia. mGluR3 is expressed by glia and neurons in many brain regions and has a predominantly presynaptic distribution, consistent with its role as an inhibitory autoreceptor and heteroceptor. mGluR3 splice variants exist in human brain but are of unknown function. Differentiation of mGluR3 from mGluR2 has been problematic because of the lack of selective ligands and antibodies; the available data suggest particular roles for mGluR3 in long-term depression, in glial function and in neuroprotection. Some but not all studies find genetic association of GRM3 polymorphisms with psychosis, with the risk alleles also being associated with schizophrenia-related endophenotypes such as impaired cognition, cortical activation and glutamate markers. The dimeric form of mGluR3 may be reduced in the brain in schizophrenia. Finally, preclinical findings have made mGluR3 a putative therapeutic target, and now direct evidence for antipsychotic efficacy of a group II mGluR agonist has emerged from a randomised clinical trial in schizophrenia. Together these data implicate mGluR3 in aetiological, pathophysiological and pharmacotherapeutic aspects of the disorder.
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Affiliation(s)
- P J Harrison
- Department of Psychiatry, University of Oxford, Neurosciences Building, Warneford Hospital, Oxford, UK.
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32
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Glutamatergic abnormalities of the thalamus in schizophrenia: a systematic review. J Neural Transm (Vienna) 2008; 115:493-511. [DOI: 10.1007/s00702-007-0859-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Accepted: 11/04/2007] [Indexed: 10/22/2022]
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Corti C, Crepaldi L, Mion S, Roth AL, Xuereb JH, Ferraguti F. Altered dimerization of metabotropic glutamate receptor 3 in schizophrenia. Biol Psychiatry 2007; 62:747-55. [PMID: 17531207 DOI: 10.1016/j.biopsych.2006.12.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Revised: 10/30/2006] [Accepted: 12/07/2006] [Indexed: 11/20/2022]
Abstract
BACKGROUND Metabotropic glutamate receptors (mGlus) may be involved in the pathophysiology of schizophrenia. Group II mGlus (mGlu2 and mGlu3) have attracted considerable interest since the development of potent specific agonists that exhibit atypical antipsychotic-like activity and reports of a genetic association between the mGlu3 gene and schizophrenia. METHODS In this postmortem study, mGlu3 protein levels in Brodmann area 10 of prefrontal cortex from schizophrenic (n = 20) and control (n = 35) subjects were analyzed by western immunoblotting using a novel specific mGlu3 antibody and an antibody for the vesicular glutamate transporter 1 (VGluT1). RESULTS We report a significant decrease in the dimeric/oligomeric forms of mGlu3 in schizophrenic patients compared with control subjects, whereas total mGlu3 and VGluT1 levels were not altered significantly. CONCLUSIONS This is the first experimental evidence that mGlu3 receptor levels are altered in schizophrenia and supports the hypothesis that neurotransmission involving this particular excitatory amino acid receptor is impaired in schizophrenia.
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Affiliation(s)
- Corrado Corti
- Department of Biology, Psychiatry Centre of Excellence in Drug Discovery, GlaxoSmithKline Medicines Research Centre, Verona, Italy.
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34
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Large CH. Do NMDA receptor antagonist models of schizophrenia predict the clinical efficacy of antipsychotic drugs? J Psychopharmacol 2007; 21:283-301. [PMID: 17591656 DOI: 10.1177/0269881107077712] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
N-methyl-D-aspartate (NMDA) receptor antagonists, such as ketamine and phencyclidine, induce perceptual abnormalities, psychosis-like symptoms, and mood changes in healthy humans and patients with schizophrenia. The similarity between NMDA receptor antagonist-induced psychosis and schizophrenia has led to the widespread use of the drugs to provide models to aid the development of novel treatments for the disorder. This review investigates the predictive validity of NMDA receptor antagonist models based on a range of novel treatments that have now reached clinical trials. Furthermore, it considers the extent to which the different hypotheses that have been proposed to account for the psychotomimetic effects of NMDA receptor antagonist have been validated by the results of these trials. Finally, the review discusses some of the caveats associated with use of the models and some suggestions as to how a greater use of translational markers might ensure progress in understanding the relationship between the models and schizophrenia.
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Affiliation(s)
- Charles H Large
- Psychiatry CEDD, GlaxoSmithKline, Via Fleming 4, 37135 Verona, Italy.
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35
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Lea PM, Faden AI. Metabotropic glutamate receptor subtype 5 antagonists MPEP and MTEP. CNS DRUG REVIEWS 2006; 12:149-66. [PMID: 16958988 PMCID: PMC6494124 DOI: 10.1111/j.1527-3458.2006.00149.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate regulates the function of central nervous system (CNS), in part, through the cAMP and/or IP3/DAG second messenger-associated metabotropic glutamate receptors (mGluRs). The mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) has been extensively used to elucidate potential physiological and pathophysiological functions of mGluR5. Unfortunately, recent evidence indicates significant non-specific actions of MPEP, including inhibition of NMDA receptors. In contrast, in vivo and in vitro characterization of the newer mGluR5 antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) indicates that it is more highly selective for mGluR5 over mGluR1, has no effect on other mGluR subtypes, and has fewer off-target effects than MPEP. This article reviews literature on both of these mGluR5 antagonists, which suggests their possible utility in neurodegeneration, addiction, anxiety and pain management.
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Affiliation(s)
| | - Alan I. Faden
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
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36
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Baracskay KL, Haroutunian V, Meador-Woodruff JH. Dopamine receptor signaling molecules are altered in elderly schizophrenic cortex. Synapse 2006; 60:271-9. [PMID: 16786528 DOI: 10.1002/syn.20292] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Alterations of molecules that mediate dopaminergic signal transduction have been found in schizophrenia, supporting the hypothesis of altered dopaminergic neurotransmission in this illness. To further explore this hypothesis, the authors measured transcript expression of three proteins involved in dopamine (DA) signaling in postmortem dorsolateral prefrontal and anterior cingulate cortex of elderly schizophrenic subjects and a comparison group. The transcript encoding calcyon, a protein that potentiates crosstalk between D1 DA receptors and Gq/11-linked receptors, was increased in schizophrenic prefrontal and cingulate cortex by 25%. Transcript levels of spinophilin, a protein enriched in dendritic spines that modulates excitatory neurotransmission, were increased 22% in dorsolateral prefrontal cortex but were unchanged in anterior cingulate cortex in schizophrenia. Levels of DARPP-32 mRNA, a downstream effector of dopaminergic neurotransmission, were similar in both groups for both cortical groups. These alterations in spinophilin and calcyon mRNA levels in schizophrenic prefrontal and cingulate cortex provide further evidence of altered dopaminergic neurotransmission in this illness.
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Affiliation(s)
- Karen L Baracskay
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan, USA
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37
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Clinton SM, Haroutunian V, Meador-Woodruff JH. Up-regulation of NMDA receptor subunit and post-synaptic density protein expression in the thalamus of elderly patients with schizophrenia. J Neurochem 2006; 98:1114-25. [PMID: 16762023 DOI: 10.1111/j.1471-4159.2006.03954.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Numerous studies have described structural and functional abnormalities of the thalamus in schizophrenia, but surprisingly few studies have examined neurochemical abnormalities that accompany these pathological changes. We previously identified abnormalities of multiple molecules associated with glutamatergic neurotransmission, including changes in NMDA receptor subunit transcripts and binding sites and NMDA receptor-associated post-synaptic density (PSD) protein transcripts in the thalamus of elderly patients with schizophrenia. In the present study, we performed western blot analysis to determine whether protein levels of NMDA receptor subunits (NR1, NR2A, NR2B) and associated PSD proteins (NF-L, PSD95, SAP102) are altered in schizophrenia. Thalamic tissue from each subject was grossly dissected into two regions: a dorsomedial region containing limbic-associated dorsomedial, anterior and central medial thalamic nuclei; and a ventral thalamus region that primarily consisted of the ventral lateral nucleus. We observed increased protein expression of the NR2B NMDA receptor subunit and its associated intracellular protein, PSD95, in the dorsomedial thalamus of patients with schizophrenia, but the other molecules were unchanged, and we found no changes in the ventral thalamus. These data provide additional evidence of thalamic neurochemical abnormalities, particularly in thalamic nuclei which project to limbic regions of the brain. Further, these findings provide additional evidence of NMDA receptor alterations in schizophrenia, which may play an important role in the neurobiology of the illness.
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Affiliation(s)
- Sarah M Clinton
- Department of Psychiatry, Molecular and Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, 48109, USA.
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38
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Bills C, Schachtman TR, Serfozo P, Spooren WPJM, Gasparini F, Simonyi A. Effects of metabotropic glutamate receptor 5 on latent inhibition in conditioned taste aversion. Behav Brain Res 2005; 157:71-8. [PMID: 15617773 DOI: 10.1016/j.bbr.2004.06.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2003] [Revised: 03/22/2004] [Accepted: 06/11/2004] [Indexed: 11/19/2022]
Abstract
Latent inhibition (LI) is a phenomenon by which pre-exposure of a conditioned stimulus (CS) prior to the CS-unconditioned stimulus (US) pairings retards conditioned responding (CR). LI has been demonstrated in a variety of learning tasks including conditioned taste aversion (CTA). Earlier work has shown that systemic administration of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective metabotropic glutamate receptor 5 (mGlu5) antagonist, is able to disrupt classical conditioning in CTA. The present study investigated the involvement of mGlu5 receptors in LI using a CTA procedure. In the first experiment, rats received either water (non-pre-exposed, NPE) or a saccharin solution (pre-exposed, PE) on 2 consecutive days. The animals then received conditioning in which a fixed amount of saccharin was paired with lithium chloride and then the CR to the taste was tested. Either MPEP (3, 6, 12 mg/kg) or vehicle was injected intraperitoneally prior to taste pre-exposure or testing. Animals in the vehicle control groups displayed LI. MPEP injections before pre-exposure trials attenuated LI but also reduced consumption during pre-exposure, which obscured interpretation of the LI effect. The second experiment used four pre-exposure trials and controlled access to fixed amount of the solutions during the pre-exposure as well as the conditioning trials. Rats were injected before pre-exposure trials but not before the test trial. The results found that MPEP attenuates latent inhibition suggesting that the mGlu5 receptor exerts an influence on the processes that underlie the effects of taste pre-exposure on conditioning.
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Affiliation(s)
- Carla Bills
- Department of Psychological Sciences, University of Missouri, Columbia, MO 65211, USA
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39
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Katsel PL, Davis KL, Haroutunian V. Large-Scale Microarray Studies of Gene Expression in Multiple Regions of the Brain in Schizophrenia and Alzheimer's Disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 63:41-82. [PMID: 15797465 DOI: 10.1016/s0074-7742(05)63003-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Pavel L Katsel
- Department of Psychiatry, The Mount Sinai School of Medicine New York, New York 10029 USA
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40
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Harrison PJ, Weinberger DR. Schizophrenia genes, gene expression, and neuropathology: on the matter of their convergence. Mol Psychiatry 2005; 10:40-68; image 5. [PMID: 15263907 DOI: 10.1038/sj.mp.4001558] [Citation(s) in RCA: 1414] [Impact Index Per Article: 74.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This review critically summarizes the neuropathology and genetics of schizophrenia, the relationship between them, and speculates on their functional convergence. The morphological correlates of schizophrenia are subtle, and range from a slight reduction in brain size to localized alterations in the morphology and molecular composition of specific neuronal, synaptic, and glial populations in the hippocampus, dorsolateral prefrontal cortex, and dorsal thalamus. These findings have fostered the view of schizophrenia as a disorder of connectivity and of the synapse. Although attractive, such concepts are vague, and differentiating primary events from epiphenomena has been difficult. A way forward is provided by the recent identification of several putative susceptibility genes (including neuregulin, dysbindin, COMT, DISC1, RGS4, GRM3, and G72). We discuss the evidence for these and other genes, along with what is known of their expression profiles and biological roles in brain and how these may be altered in schizophrenia. The evidence for several of the genes is now strong. However, for none, with the likely exception of COMT, has a causative allele or the mechanism by which it predisposes to schizophrenia been identified. Nevertheless, we speculate that the genes may all converge functionally upon schizophrenia risk via an influence upon synaptic plasticity and the development and stabilization of cortical microcircuitry. NMDA receptor-mediated glutamate transmission may be especially implicated, though there are also direct and indirect links to dopamine and GABA signalling. Hence, there is a correspondence between the putative roles of the genes at the molecular and synaptic levels and the existing understanding of the disorder at the neural systems level. Characterization of a core molecular pathway and a 'genetic cytoarchitecture' would be a profound advance in understanding schizophrenia, and may have equally significant therapeutic implications.
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Affiliation(s)
- P J Harrison
- Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, UK.
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41
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Clinton SM, Meador-Woodruff JH. Thalamic dysfunction in schizophrenia: neurochemical, neuropathological, and in vivo imaging abnormalities. Schizophr Res 2004; 69:237-53. [PMID: 15469196 DOI: 10.1016/j.schres.2003.09.017] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While abnormalities of the prefrontal cortex and temporal lobe structures have typically been associated with the pathophysiology of schizophrenia, recent findings implicate thalamic dysfunction in this illness as well. The thalamus plays a critical role in processing and integrating sensory information relevant to emotional and cognitive functions. Neuropathological and in vivo imaging studies in schizophrenia have identified several structural and metabolic abnormalities in the thalamus, which may contribute to a deficit in sensory processing and be related to psychotic symptomatology. In addition to these postmortem and in vivo imaging studies indicating structural and metabolic changes in the thalamus in schizophrenia, more recent studies have examined the neurochemical substrates that accompany these changes. Much of this work to date has focused on glutamatergic abnormalities in the thalamus, in part because it is a predominant neurotransmitter used in the thalamus, and because glutamatergic dysfunction has been hypothesized to be involved in schizophrenia. Several studies, however, have also examined markers of gamma-aminobutyric acid (GABA) and dopaminergic neurotransmission in the thalamus in schizophrenia. We review these neurochemical findings, as well as the growing body of postmortem and in vivo imaging evidence that supports the hypothesis of thalamic dysfunction in schizophrenia.
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Affiliation(s)
- Sarah M Clinton
- Department of Psychiatry and Mental Health Research Institute, University of Michigan Medical School, 205 Zina Pitcher Place, Ann Arbor, MI 48109-0720, USA.
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42
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Clinton SM, Meador-Woodruff JH. Abnormalities of the NMDA Receptor and Associated Intracellular Molecules in the Thalamus in Schizophrenia and Bipolar Disorder. Neuropsychopharmacology 2004; 29:1353-62. [PMID: 15054476 DOI: 10.1038/sj.npp.1300451] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Several lines of investigation support a hypothesis of glutamatergic dysfunction in schizophrenia, including our recent reports of altered NMDA receptor subunit and associated intracellular protein transcripts in the thalamus of elderly patients with schizophrenia. In the present study, we used in situ hybridization to measure the expression of NMDA subunits (NR1, NR2A-D), and associated intracellular proteins (NF-L, PSD95, and SAP102) in a second, younger cohort from the Stanley Foundation Neuropathology Consortium, which included patients with both schizophrenia and affective disorders. We wanted to determine whether glutamatergic abnormalities in the thalamus in schizophrenia are present at younger ages, and whether these abnormalities occur in other psychiatric illnesses. In the present work, we observed increased expression of NMDA NR2B subunit transcripts, and decreased expression of all three associated postsynaptic density protein transcripts in schizophrenia. We also found evidence of glutamatergic dysfunction in the thalamus in affective disorders, particularly in bipolar disorder. In particular, we found decreased NF-L, PSD95, and SAP102 transcripts in bipolar disorder, and decreased SAP102 levels in major depression. Interestingly, one of the most consistent findings across diagnostic groups was an abnormality of intracellular signaling molecules that are linked to the NMDA receptor, rather than changes in the receptor subunits themselves. PSD95 and similar scaffolding molecules link the NMDA receptor with intracellular enzymes that mediate signaling, and also provide a physical link between different neurotransmitter systems to coordinate and integrate information from multiple effector systems. Abnormalities of PSD95-like molecules and other intracellular signaling machinery may contribute to dysregulated communication between multiple neurotransmitter systems (such as glutamatergic and dopaminergic systems) that are potentially involved in the neurobiology of schizophrenia and affective disorders.
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Affiliation(s)
- Sarah M Clinton
- Department of Psychiatry, Mental Health Research Institute, University of Michigan Medical School, Ann Arbor, MI 48109-0720, USA.
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43
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Meador-Woodruff JH, Clinton SM, Beneyto M, McCullumsmith RE. Molecular Abnormalities of the Glutamate Synapse in the Thalamus in Schizophrenia. Ann N Y Acad Sci 2003; 1003:75-93. [PMID: 14684436 DOI: 10.1196/annals.1300.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Schizophrenia has been associated with dysfunction of glutamatergic neurotransmission. Synaptic glutamate activates pre- and postsynaptic ionotropic NMDA, AMPA, and kainate and metabotropic receptors, is removed from the synapse via five cell surface-expressed transporters, and is packaged for release by three vesicular transporters. In addition, there is a family of intracellular molecules enriched in the postsynaptic density (PSD) that target glutamate receptors to the synaptic membrane, modulate receptor activity, and coordinate glutamate receptor-related signal transduction. Each family of PSD proteins is selective for a given glutamate receptor subtype, the most well characterized being the NMDA receptor binding proteins PSD93, PSD95, NF-L, and SAP102. Besides binding glutamate receptors, many of these proteins also interact with cell surface proteins like cell adhesion molecules, ion channels, cytoskeletal elements, and signal transduction molecules. Given the complexity of the glutamate neurotransmitter system, there are many locations where disruption of normal signaling could occur and give rise to abnormal glutamatergic neurotransmission in schizophrenia. Using multiple cohorts of postmortem tissue, we have examined these synaptic molecules in schizophrenic thalamus. The expression of NR1 and NR2C subunit transcripts is decreased in the thalamus in schizophrenia. Interestingly, three intracellular PSD molecules that link the NMDA receptor to signal transduction pathways are also abnormally expressed. Additionally, several of the cell surface and vesicular transporters are abnormal in the schizophrenic thalamus. While occasional findings of abnormal receptor expression are made, the most dramatic and consistent alterations that we have found in the thalamus in schizophrenia involve the family of intracellular signaling/scaffolding molecules. We propose that schizophrenia has a glutamatergic component that involves alterations in the intracellular machinery that is coupled to glutamate receptors, in addition to abnormalities of the receptors themselves. Our data suggest that schizophrenia is associated with abnormal glutamate receptor-related intracellular signaling in the thalamus, and point to novel targets for innovative drug discovery.
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Affiliation(s)
- James H Meador-Woodruff
- Mental Health Research Institute and Department of Psychiatry, University of Michigan, Ann Arbor, Michigan 48109-0720, USA.
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44
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Fukumaki Y, Shibata H. Glutamate receptor genes as candidates for schizophrenia susceptibility. Drug Dev Res 2003. [DOI: 10.1002/ddr.10293] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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45
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Haroutunian V, Dracheva S, Davis KL. Neurobiology of glutamatergic abnormalities in schizophrenia. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1566-2772(03)00020-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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46
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Konradi C, Heckers S. Molecular aspects of glutamate dysregulation: implications for schizophrenia and its treatment. Pharmacol Ther 2003; 97:153-79. [PMID: 12559388 PMCID: PMC4203361 DOI: 10.1016/s0163-7258(02)00328-5] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The glutamate system is involved in many aspects of neuronal synaptic strength and function during development and throughout life. Synapse formation in early brain development, synapse maintenance, and synaptic plasticity are all influenced by the glutamate system. The number of neurons and the number of their connections are determined by the activity of the glutamate system and its receptors. Malfunctions of the glutamate system affect neuroplasticity and can cause neuronal toxicity. In schizophrenia, many glutamate-regulated processes seem to be perturbed. Abnormal neuronal development, abnormal synaptic plasticity, and neurodegeneration have been proposed to be causal or contributing factors in schizophrenia. Interestingly, it seems that the glutamate system is dysregulated and that N-methyl-D-aspartate receptors operate at reduced activity. Here we discuss how the molecular aspects of glutamate malfunction can explain some of the neuropathology observed in schizophrenia, and how the available treatment intervenes through the glutamate system.
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Affiliation(s)
- Christine Konradi
- Department of Psychiatry, Harvard Medical School, Boston, MA 02115, USA.
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47
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Abstract
The first choice group of psychotropic agents in schizophrenia is neuroleptics. However, this treatment is not effective in all patients and with every symptom. We summarize papers published on the role of antiepileptic drugs in treatment-resistant schizophrenia. We have searched the computer database system MEDLINE for relevant articles including reviews, reports of drug studies and case histories. Antiepileptic drugs can change symptoms of schizophrenia by their action on GABA-ergic neurotransmission or via anti-glutamatergic mechanisms. High doses of adjunctive benzodiazepines reduce positive symptoms, anxiety, and agitation. Carbamazepine is effective in affective symptoms of schizophrenia and influences violent behavior in psychotic patients. Its anti-kindling action may represent a promising treatment strategy for some patients with chronic course of schizophrenia. Valproate treatment leads to a decrease in positive symptoms as well as hostility. Lamotrigine is expected to influence the positive, negative, affective, and cognitive symptoms of schizophrenia. New antiepileptics (e.g., gabapentin, oxcarbazepine, topiramate, vigabatrin) present a promise as potential adjuncts to neuroleptic treatment in resistant symptoms of schizophrenia.
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Affiliation(s)
- L Hosák
- Department of Psychiatry, Charles University School of Medicine, 500 05 Hradec Králové, Czech Republic.
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48
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Crook JM, Akil M, Law BCW, Hyde TM, Kleinman JE. Comparative analysis of group II metabotropic glutamate receptor immunoreactivity in Brodmann's area 46 of the dorsolateral prefrontal cortex from patients with schizophrenia and normal subjects. Mol Psychiatry 2002; 7:157-64. [PMID: 11840308 DOI: 10.1038/sj.mp.4000966] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2001] [Revised: 05/16/2001] [Accepted: 06/27/2001] [Indexed: 11/09/2022]
Abstract
Glutamate is the primary excitatory neurotransmitter in the mammalian central nervous system, and a key neurotransmitter in prefrontal cortical function. Converging lines of evidence implicate prefrontal cortical dysfunction in the neurobiology of schizophrenia. Thus, aberrant glutamate neurotransmission may underlie schizophrenia and other complex disorders of behavior. Group II metabotropic receptors (mGluRs) are important modulators of glutamatergic and non-glutamatergic neurotransmission. Moreover, in an animal model, an agonist for group II mGluRs has been shown to reverse the behavioral, locomotor, and cognitive effects of the psychotomimetic drug phencyclidine. Accordingly, group II mGluRs constitute attractive targets for the pharmacotherapeutics and study of schizophrenia. Using immunocytochemistry and Western immunoblotting, we compared the localization and levels of group II mGluRs in Brodmann's area 46 of the dorsolateral prefrontal cortex from patients with schizophrenia and normal subjects. Consistent with previous reports, we found that immunolabeling of group II mGluRs is prominent in Brodmann's area 46. The majority of labeling was present on axon terminals distributed in a lamina-specific fashion. No apparent difference in the cellular localization or laminar distribution of immunoreactive group II mGluRs was noted between the two diagnostic groups. Similarly, the levels of receptor immunoreactivity determined by quantitative Western immunoblotting were comparable between schizophrenic patients and normal subjects. We conclude that while the function of group II mGluRs in Brodmann's area 46 of dorsolateral prefrontal cortex may be altered in patients with schizophrenia, this is not evident at the level of protein expression using an antibody against mGluR2 and mGluR3.
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Affiliation(s)
- J M Crook
- Section on Neuropathology, Clinical Brain Disorders Branch, National Institute of Mental Health, Bethesda, MD 20892, USA
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49
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Lea PM, Faden AI. Traumatic brain injury: developmental differences in glutamate receptor response and the impact on treatment. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2002; 7:235-48. [PMID: 11754517 DOI: 10.1002/mrdd.1033] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Perinatal brain injury following trauma, hypoxia, and/or ischemia represents a substantial cause of pediatric disabilities including mental retardation. Such injuries lead to neuronal cell death through either necrosis or apoptosis. Numerous in vivo and in vitro studies implicate ionotropic (iGluRs) and metabotropic (mGluRs) glutamate receptors in the modulation of such cell death. Expression of glutamate receptors changes as a function of developmental age, with substantial implications for understanding mechanisms of post-injury cell death and its potential treatment. Recent findings suggest that the developing brain is more susceptible to apoptosis after injury and that such caspase mediated cell death may be exacerbated by treatment with N-methyl-D-aspartate receptor antagonists. Moreover, group I metabotropic glutamate receptors appear to have opposite effects on necrotic and apoptotic cell death. Understanding the relative roles of glutamate receptors in post-traumatic or post-ischemic cell death as a function of developmental age may lead to novel targeted approaches to the treatment of pediatric brain injury.
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Affiliation(s)
- P M Lea
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
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50
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Dean B. Understanding the pathology of schizophrenia: recent advances from the study of the molecular architecture of postmortem CNS tissue. Postgrad Med J 2002; 78:142-8. [PMID: 11884695 PMCID: PMC1742312 DOI: 10.1136/pmj.78.917.142] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The use of central nervous system (CNS) tissue obtained postmortem has long underpinned efforts to understand the neurobiology of schizophrenia, but the ability to use such tissue in conjunction with a wide variety of methodologies has seen a renaissance of interest in this area of research. Recent findings have shown changes in markers in a number of neurotransmitter systems in the brains of subjects with schizophrenia which include the dopaminergic, serotonergic, cholinergic, glutamatergic, and GABAergic systems of the CNS. Many of these changes also appear to be regionally specific, and abnormalities in non-neurotransmitter specific pathways have been found in schizophrenia. Changes in the neurotransmitter release pathways in schizophrenia may be important in the pathology of the illness, and recent findings suggest that abnormalities in the Wnt pathway, which controls transcription selectivity in cells, may be involved. Studies using CNS material obtained postmortem clearly show that the pathology of schizophrenia is complex while the polygenetic nature of the illness may be adding to this complexity.
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Affiliation(s)
- B Dean
- Cooper Research Laboratories, The Mental Health Research Institute of Victoria, Victoria, Australia.
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